Scientists have found the unmistakable presence of certain isotopes in an iron meteorite. Since these meteorites are thought to leftover bits of planetary cores, similar isotopes must be in the Earth’s own core. And the only place to get those isotopes is from the solar wind.
Our sun constantly churns out a steady drizzle of charged particles. It’s called the solar wind, and it’s usually made of electrons, but occasionally something heavier can come out. Indeed, in our solar system, the only way to get certain isotopes of helium and iron is through the solar wind.
Prof. Dr Mario Trieloff, head of the Geo- and Cosmochemistry research group at the University of Heidelberg, and his is team looked for these isotopes in the Washington County meteorite. That meteorite fell to Earth about 100 years in Colorado, USA. The Washington County meteorite is an iron-type meteorite, which represent less than 5% of all meteorite falls.
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Iron-type meteorites are thought to be broken-off bits of old protoplanetary cores. When our solar system was much younger, it was filled with dozens, even hundreds, of almost-planets. Most of them crashed together to make the family of eight that we know today, but some got smashed to pieces.
The research team found the unmistakable presence of helium and iron isotopes in that sample, which was no easy task. According to Dr. Manfred Vogt, a member of the Trieloff team, ”the measurements had to be extraordinarily accurate and precise to differentiate the solar signatures from the dominant cosmogenic noble gases and atmospheric contamination”.
The only way for the meteorite to have those isotopes is if it absorbed them from the solar wind 4.5 billion years ago. And if that protoplanetary core did it, then so did the Earth.
The results explain why igneous rocks formed from deep mantle plumes in Hawaii and Réunion also share these isotopes: the mantle plumes are deep enough to draw those isotopes all the way from the Earth’s core.